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Integrated high-performance and accurate shaping technology of low-cost powder metallurgy titanium alloys: A comprehensive review

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International Journal of Minerals,Metallurgy and Materials 2024年第3期31卷 413-426页

作者： Xuemeng gan Shaofu Li Shunyuan Xiao Yafeng Yang State Key Laboratory of Mesoscience and Engineering Institute of Process EngineeringChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Science and Technology on Particle Materials Chinese Academy of SciencesBeijing 100190China

The practical engineering applications of powder metallurgy (PM) Ti alloys produced through cold compaction and pressure-less sintering are impeded by poor sintering densification, embrittlement caused by excessive O impurities, and severe sintering deforma-tion resulting from the use of heterogeneous powder mixtures. This review presents a summary of our previous work on addressing the above challenges. Initially, we proposed a novel strategy using reaction-induced liquid phases to enhance sintering densification. Near- complete density (relative density exceeding 99%) was achieved by applying the above strategy and newly developed sintering aids. By focusing on the O-induced embrittlement issue, we determined the onset dissolution temperature of oxide films in the Ti matrix. On the basis of this finding, we established a design criterion for effective O scavengers that require reaction with oxide films before their dissol-ution. Consequently, a ductile PM Ti alloy was successfully obtained by introducing 0.3wt% NdB6 as the O scavenger. Lastly, a powder- coating strategy was adopted to address the sintering deformation issue. The ultrafine size and shell-like distribution characteristics of coating particles ensured rapid dissolution and homogeneity in the Ti matrix, thereby facilitating linear shrinkage during sintering. As a result, geometrically complex Ti alloy parts with high dimensional accuracy were fabricated by using the coated powder. Our fundament-al findings and related technical achievements enabled the development of an integrated production technology for the high-performance and accurate shaping of low-cost PM Ti alloys. Additionally, the primary engineering applications and progress in the industrialization practice of our developed technology are introduced in this review.

关键词： powder metallurgy titanium sintering densification oxygen scavenging accurate shaping

Baseflow Characteristics in Alpine Rivers-a Multicatchment Analysis in Northwest China

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Journal of Mountain Science 2015年第3期12卷 614-625页

作者： gan Rong SUN Lin LUO Yi Key Laboratory of Ecosystem Network Observation and Modeling Institute of Geographic Sciences and Natural Resources ResearchChinese Academy of Sciences University of Chinese Academy of Sciences

As a component of streamflow, baseflow is critical for regulating seasonal distribution of river fows and stabilizing water supplies. Water resources in the arid area of Northwest China are mainly from multiple catchments in the alpine that could be influenced by varieties of climatic, land cover, soil and geological factors. While numerous studies have been done on streamflow, systematic analysis of baseflow in the alpine river systems is scare. Based on historical daily streamflow data and the automated digital filter method of baseflow separation, this study investigated characteristics of hydrographs of overland flow, streamflow and baseflowof river systems fed by rainfall, snowmelt, glacier melt or mixtures of these. This study also calculated the recession constants and baseflow indices of 65 river systems. While the recession constant was ***34- o.o728 with a mean of o.o18, the baseflow index was 0.27-0.79 with a mean of 0.57. Further, Spearman＇s correlation analysis showed that the baseflow index was significantly correlated with catchment climatic factors （e.g., precipitation and temperature）, topographic factors （e.g., elevation and slope） and aquifer properties represented by the recession constant. Multiple regression analysis indicated that the factors explained 65% of the variability of baseflow index in the studv area.

关键词： Baseflow index Recession constant Snowmelt Glacier melt Streamflow

Twisted Helical Microfibers by Hierarchical Self-Assembly of an Aromatic Oligoamide Foldamer

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Chinese Journal of Chemistry 2013年第5期31卷 651-656页

作者： Quan gan Ying Wang Hua Jiang College of Chemistry Beijing Normal University Beijing 100875 China Beijing National Laboratory for Molecular Sciences CAS Key Laboratory of Photochemistry Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China

A series of aromatic oligoamide foldamers based on 8-fluoro amino-quinoline carboxyl acid have been synthe- sized and characterized. Studies show that these foldamers self-assemble to form well-defined twisted helical mi- crofibers in chloroform-methanol （1 ： 1, V/V） binary solvent due to the intermolecular π-π stacking and van der Waals forces of aliphatic chains, which are supported by SEM, TEM and XRD. It is also revealed that the assembly morphologies show strong dependence on the length of alkyl chains.

关键词： foldamer self-assembly microfiber hydrogen bonding aromatic stacking

New Splitting Algorithms for Multiplicative Noise Removal Based on Aubert-Aujol Model

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Numerical Mathematics(Theory,Methods and Applications) 2022年第2期15卷 415-441页

作者： Yu gan Jie Zhang Huibin Chang School of Mathematical Sciences Tianjin Normal UniversityTianjinChina Department of Mathematics The University of Hong KongHong KongSARChina

In this paper,we propose new algorithms for multiplicative noise removal based on the Aubert-Aujol(AA)*** introducing a constraint from the forward model with an auxiliary variable for the noise,the NEMA(short for Noise Estimate based Multiplicative noise removal by alternating direction method of multipliers(ADMM))is firstly *** further reduce the computational cost,an additional proximal term is considered for the subproblem with regard to the original variable,the NEMA_(f)(short for a variant of NEMA with fully splitting form)is further *** conduct numerous experiments to show the convergence and performance of the proposed ***,the restoration results by the proposed algorithms are better in terms of SNRs for image deblurring than other compared methods including two popular algorithms for AA model and three algorithms of its convex variants.

关键词： Alternating direction method of multipliers image denoising and deblurring multiplicative noise total variation

Transcriptional regulatory circuits controlling muscle fiber type switching

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Science China(Life Sciences) 2015年第4期58卷 321-327页

作者： LIU Jing LIANG XiJun gan ZhenJi MOE Key Laboratory of Model Animal for Disease Study Model Animal Research Center Nanjing University

Skeletal muscle fitness plays vital roles in human health and disease and is determined by developmental as well as physiological inputs. These inputs control and coordinate muscle fiber programs, including capacity for fuel burning, mitochondrial ATP production, and contraction. Recent studies have demonstrated crucial roles for nuclear receptors and their co-activators, and micro RNAs(mi RNAs) in the regulation of skeletal muscle energy metabolism and fiber type determination. In this review, we present recent progress in the study of nuclear receptor signaling and mi RNA networks in muscle fiber type switching. We also discuss the therapeutic potential of nuclear receptors and mi RNAs in disease states that are associated with loss of muscle fitness.

关键词： fiber type switching gene regulation muscle nuclear receptor microRNA

In situ evaluation of cell cultivation on dynamically changed poly(ε-caprolactone) film caused by enzymatic degradation

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Science China Chemistry 2011年第2期54卷 369-374页

作者： ZHANG Yu JIANG Ni gan ZhiHua Key Laboratory of Engineering Plastics Institute of Chemistry Chinese Academy of Sciences Beijing 100190 China

In situ evaluation of cell cultivation on degrading poly(ε-caprolactone) (PCL) films was *** culture surroundings were constructed for cell growth by using PCL films as substrates and adding Pseudomonas cepacia lipase to accelerate biodegradation of PCL *** experiments for 10 h indicated the low cytotoxicity of lipase solution with concentration up to 0.2 mg/mL for MG-63 cells growth on PCL *** the optimized lipase concentration and degradation time,we studied cell growth behavior on dynamically changed PCL films by adding lipase to the culture ***,fluorescence microscopy and scanning electron microscopy (SEM) were used to evaluate cell viability,proliferation and *** was found that cell viability and proliferation were not affected by the added lipase solution *** contrast,cells cultured on degrading PCL films showed good growth behavior with clear fusiform shape and ***,the enzymatic degradation of PCL films with cells attachment showed distinctive morphology compared to the degradation in lipase solution without *** simultaneous cell growth and PCL film degradation were well discussed in this work,which may better understand the interaction between cell growth and polymer degradation.

关键词： poly(ε-caprolactone) film enzymatic degradation cell growth surface morphology

Differences in the Rainfall Characteristics between Mount Tai and Its Surrounding Areas

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Journal of Meteorological Research 2019年第5期33卷 976-988页

作者： Yuting gan Nina LI Jian LI Chinese Academy of Meteorological Sciences China Meteorological Administration

As a typical small-scale, isolated topography, Mount Tai exhibits great differences in precipitation characteristics from the surrounding areas. It was found that the amount of rainfall occurring over Mount Tai is significantly larger than what is observed in the surrounding areas. Based on hourly rain gauge records for the warm season(May to September) of 1996–2015, differences between Mount Tai and its surrounding areas were further revealed in terms of rainfall diurnal variation, spatial scale, and evolution process. The diurnal variation of the enhancement on rainfall amount exhibit "dual peaks" occurring in the early morning and afternoon, and the dual peaks are mainly attributable to rainfall frequency. The diurnal phase of the rainfall amount in the surrounding areas lags 1 h behind that over Mount Tai. Regarding differences in rainfall spatial scale, compared to those of surrounding areas, precipitation over Mount Tai is characterized by a smaller coverage, especially in the early morning. Mount Tai also tends to have a kind of unique, small-scale rainfall in the afternoon and at night. Based on statistical analysis of precipitation events,differences in rainfall evolution process were identified as well. Rainfall over Mount Tai often starts earlier in the afternoon and ends later at night than it does in the surrounding areas. Furthermore, nocturnal rainfall events over Mount Tai are prone to peaking over a shorter period and enduring for a longer period after reaching their maximum intensity, compared with nocturnal rainfall events occurring in the surrounding areas. Rainfall events over Mount Tai always last longer, especially those occurring in the early morning. In general, Mount Tai has a large enhancement effect on rainfall.

关键词： rainfall differences diurnal variation rainfall evolution process isolated topography Mount Tai

RNA interference with DNA polymerase and synthesis

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Science China Chemistry 2014年第7期57卷 954-960页

作者： ABDUR Rob gan JianHua HUANG Zhen Department of Chemistry Georgia State University

RNA can catalyze and participate in many chemical and biochemical reactions. Non-coding RNAs （ncRNA） can regulate cellular transcription and translation reactions. We have demonstrated biochemically that RNA can also interfere with DNA polymerization via transforming DNA polymerase into deoxyribonucleoside triphosphate diphosphatase （dNTP-DPase）. RNA, even with six nucleotides, can transform DNA polymerase into dNTP-DPase, and the dNTP-DPase activity causes the hydrolysis of dNTPs into dNMPs and pyrophosphate. Moreover, we have found that DNA polymerases from several families generally have similar RNA-dependent dNTP-DPase activity. We have also observed that in the presence of RNA, when the dNTP concentrations are relatively low, and that the dNTP-DPase activity can deplete dNTPs and interfere with DNA polymerization Thus, we have discovered for the first time that in the presence of RNA, DNA polymerase can behave as a diphosphatase and inhibit DNA synthesis when dNTP quantity is low. These in vitro observations might imply a plausible role of RNA in vivo, such as suppressing DNA synthesis during a resting phase （Go） of the cell cycle, when RNA quantity is high and dNTP quantity is low.

关键词： RNA interference alternative activity of DNA polymerase non-coding RNA deoxyribonucleoside triphosphatediphosphatase DNA polymerization and synthesis

Structure of Strict Abundant Semigroups

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Algebra Colloquium 2019年第3期26卷 387-400页

作者： Yizhi Chen Bo Yang Aiping gan School of Mathematics and Big Data Huizhou University HuizhouGuangdong 516007China No.1 Senior School of Liantang Nanchang 330200China College of Mathematics and Information Science Jiangxi Normal University Nanchang 330022China

We introduce a new class of semigroups called strict abundant semigroups,which are concordant semigroups and subdirect products of completely-J*-simple abundant semigroups and completely-J*-simple primitive abundant semigroups.A general construction and a tree structure of such semigroups are ***,the corresponding structure theorems for strict regular semigroups given by Auinger in 1992 and by Grillet in 1995 are generalized and ***,an example of strict abundant semigroups is also given.

关键词： structure regular semigroup strict regular semigroup abundant semigroup strict abundant semigroup